Continuous catheter flushing apparatus

ABSTRACT

An apparatus effecting continuous flushing of intravascular catheters in systems for monitoring conditions in the thoracic cavity during surgery in the intensive care ward, cardio vascular diagnostic laboratories, etc. The apparatus embodies a small block having therein passages for a flushing solution in one of which is a flow resistor to limit the flushing to a small amount, a fail-safe valve in another passage connected by a bypass to the first passage for fast flushing with a much larger amount of solution, and means for connecting the catheter to a monitoring apparatus.

United States Patent Reynolds et al.

[54] CONTINUOUS CATHETER FLUSHING APPARATUS [72] Inventors: Gordon S.Reynolds; Karl A. Pannier, Jr.; James L. Sorenson, all of Salt LakeCity,

Utah

[73] Assignee: Le Voy's, Inc., Salt Lake City, Utah [22] Filed: Sept.18, 1970 21 Appl. No.: 73,314

[52] US. Cl. ..25l/117, 128/214 F, 128/214 R, 251/335 R [51] Int. Cl...Fl6k 51/00, A61m 5/00 [58] FieldoiSearch ..251/117, 38, 335; 128/214F, 128/214 R [56] References Cited UNITED STATES PATENTS 2,229,9031/1941 Schmohletal. ..25l/117X 1 July 11,1972

Quinn ..25l/333 R X Hall et al.. ..25l/l 17 Langdon ..251/38 Bergman..,.128/2l4 R Primary Examinerl-lenry T. Klinksiek Attorney-Hill,Sherman, Meroni, Gross & Simpson 57 ABSTRACT An apparatus effectingcontinuous flushing of intravascular catheters in systems for monitoringconditions in the thoracic cavity during surgery in the intensive careward, cardio vascular diagnostic laboratories, etc. The apparatusembodies a small block having therein passages for a flushing solutionin one of which is a flow resistor to limit the flushing to a smallamount, a fail-safe valve in another passage connected by a bypass tothe first passage for fast flushing with a much larger amount ofsolution, and means for connecting the catheter to a monitoringapparatus.

10 Claims, 5 Drawing Figures CONTINUOUS CATHETER FLUSI-IING APPARATUSSUMMARY OF THE INVENTION Catheter cannulation of an artery or a vein forpressure monitoring, particularly of central pressure in the thoraciccavity, has become an indispensable technique in modern hospitals. Forexample, from a central arterial catheter introduction system and acontinuous and intemiittent flush system which allow high qualityclinical recording of central arterial pulse waveforms, it is possibleto measure a number of parameters from the central pulse contour. Suchparameters include stroke volume, heart rate, cardiac output, durationof systole, and systolic, diastolic and mean pressures. In addition,blood for intermittent arterial blood gas analysis can be withdrawn.

It has been found necessary to continuously flush the catheter toprevent occlusion of the intravascular catheter end by blood clotting,and maintain catheter patency for continuous recording over periodswhich may amount to several days. Continuous flushing systems utilizingmarine-bore capillary tubes as flow resistors and applying the flushingsolution under pressure have heretofore been devised, one such beingdescribed in an article appearing on pages 675-678 of the Journal ofThoracic and Cardiovascular Surgery, Volume 57, No. 5, May, 1969.Formerly known systems for the intended purposes embodied anobjectionably large amount of apparatus complicated to set up and theseformer systems presented a major problem in maintaining a high qualityof pulse waveform. That resulted in a loss of fidelity of recording dueto clots and high viscosity blood being in the catheter system, and thelargest contributor to this problem was stopcocks, a number of whichwere used in every prior system of which we are aware. Stopcocks haveminute leaks, and although great pains were taken to maintain highquality stopcock integrity, it was found that that was almost impossibleto achieve in practice. Even with a perfect stopcock system there isstill a small volume displaced with each pressure pulse, and, therefore,a small amount of blood enters the catheter tip with each pressurepulse, and evenwith a perfectly tight system it was virtually impossibleto keep blood out of the tip of the catheter. Blood once entering thetip of the catheter, can then, by a process of diffusion, penetratefurther and further into the catheter and finally an occlusion resultsand pressure pulse fidelity decreases. Further, if the system were to befilled in a reasonable time, which is essential before operation canbegin, an additional stopcock and fluid source was required.

The instant invention overcomes the foregoing deficiencies in theprovision of a small unitary piece of apparatus for connection in thecatheter flushing system and which is so constructed so as to eliminatethe use of all stopcoc-ks in that flushing system. The instant inventionincludes a resilient valve controlling a bypass around the flow resistorand this valve is leak-proof, fail-safe, and quick acting and permitsthe measurement of dynamic characteristics of a catheter transducersystem, that is, allowing fast shut-off for square wave testing of acatheter system on an oscilloscope or the like. With this simple form ofstructure, much of the apparatus along with a complicated setup,heretofore required, has been eliminated. Consequently, with the instantinvention, it is possible to monitor the central arterial pulse waveformwith its various derived parameters with much greater ease, flexibility,and accuracy than was heretofore possible. The reliability of thepressure measuring system has been increased and the competence 'of thenurses, physicians and auxiliary personnel in determining the patientsvital signs and conditions from the central arterial waveform have alsobeen materially increased.

Other objects, features and advantages of the invention will be readilyapparent from the following description of a preferred embodimentthereof, taken in conjunction with the accompanying drawing althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts of the disclosure.

FIG. 1 is a diagrammatic disclosure illustrating a device embodyingprinciples of the instant invention in operative association with acatheter cannulated patient and a source of flushing solution, thedevice itself being exaggerated in the showing for purposes of clarity;

FIG. 2 is an enlarged central vertical sectional view through the deviceitself, with the valve in closed position;

FIG. 3 is a transverse sectional view taken substantially as indicatedby the line III-III of FIG. 2;

FIG. 4 is a plan sectional view taken substantially as indicated by theline IV-IV of FIG. 2; and

FIG. 5 is a view similar to FIG. 2 but showing the valve in openposition.

DETAILED DESCRIPI'ION'OF THE PREFERRED EMBODIMENT While the instantinvention may be incorporated in various catheter systems and even incertain other systems for the purpose of governing flow through thesystem, and is highly useful in systems for monitoring venous andarterial pressures, by way of example, the system is shown and will bedescribed herein with regard to a catheter system for. monitoringcentral arterial pressure and permit high quality clinical recording ofcentral arterial pulse waveforms. The catheter used in such a system isa thin catheter having an inside diameter in the neighborhood ofone-half a millimeter and which is preferably made ofpolytetrafluoroethylene. Such a catheter must be kept patent during useby preventing the formation of a blood clot or other occlusion at thebody end of the catheter and sufficient infusion solution must becontinuously passed through the catheter for that purpose, but not insuch amount as to be harmful to a patient during a relatively longperiod of monitoring. It has been detennined that in the case of aninfant 1 cc. of infusion solution per hour is sufficient, and in thecase of an adult 2 to 3 cc. per hour of solution is sufficient. Accuracyof the system must therefor be insured at all times, but at the sametime means must be provided to establish a rapid flush in the firstinstance to clear out the system of all air and till the system quickly,and a rapid flush is necessary from time to time to check the dynamicsof the entire system in a manner to avoid deceiving the observer andconfusing the records.

With the foregoing in mind, in FIG. 1 we have given a diagrammaticshowing of a control device I embodying principles of the presentinvention installed in a system for monitoring cardiovascular pressure.The overall system includes a pressurized infusion container 2 connectedby a tube 3 to a micron filter 4 which prevents clogging of the flowresistance element to be later described and eliminates bacteria thatmay be in the infusion solution, the filter being connected to one endof a tube 5, the other end of which is securely afiixed in the device 1.The device is also provided with a fitting 6 to which the catheter 7 isconnected. In the illustrated showing the catheter is advanced into thethoracic cavity of a patient 8 by way of entrance into the radialartery. Another fitting 9 is provided on the device I for connection toan indicating mechanism such as a manometer, as diagrammaticallyindicated at 10, or to a pressure transducer associated with anoscilloscope, or the fitting may be equipped with a self-sealing plugfor hypodermic injection in case such becomes indicated. It will beunderstood that the instant invention is usable in catheter systemswherein the catheter may be entered into various veins or arteries ofthe body. a

The device 1 may be fabricated of several parts molded of rigid plasticmaterial, preferably transparent, and the parts may be secured togethercementitiously, by fusing or welding, with the use of a solvent, or inany other suitable manner. In the illustrated showing the deviceconsists of a housing in the form of a block composed of a body 11, anend cap 12 carrying the catheter fitting 6, and an opposite end cap 13carrying the fitting 9 as well as other points of entry into passages inthe body. When it is considered that the body and end caps, exclusive ofthe fittings 6 and 9, may be sized as little as seveneighths inch long,three-quarter inches wide, and one-quarter inch thick, the advantage ofthe instant invention in eliminating apparatus utilized herebefore,including all stopcocks, in providing an easily connectable structureand one which may be suspended from the tubing since it weighs extremelylittle, and performs all the above desired operations in controllingflow through the system, will be at once appreciated.

The body 11 is molded to provide a passage 14 connecting the hollowfittings 7 and 9, the fitting 9 being internally shaped as indicated at15 to provide a connection for a Luer fitting. Another and largerpassage 16 is provided in the body 11 and cap 13 and this passagecommunicates with a cross-passage 17 by way of a reduced outlet opening18, the passage 17 connecting at one end with the aforesaid passage 14.Still a further passage 19 is provided in the body 11 and the inner endof the passage 19 tapers inwardly to a reduced size 20 and establishes avalve seat at 21, the reduced passage 20 also communicating with thecross-passage 17. Along the side of the passage 19 nearest the passage16 a small bypass passage 22 is provided in open communication with thepassage 19 and this passage connects with the passage 16 by way of aside branch 22. The aforesaid tube 5 for connection to the infusionsystem has its end portion permanently connected inside the passage 16,the cap 13 being provided with a stop element 23 thereon to prevent thetube from blocking the branch passage 22 when the tube is initiallybeing assembled to the cap 13.

Within the passage 16 is a flow resistance in the form of a tube 24having a resilient apertured sealing washer 25 at each end thereof. Theresistance 24 is what is referred to as a marine-bore tube and theactual bore 26 through the tube is but several hundredths of amillimeter in diameter so as to afford a high resistance to the flow ofinfusion solution through the resistance element. It will be appreciatedthat the showing in the drawing is highly exaggerated insofar as theinstant invention is concerned for purposes of clarity since the bore 26in the tube 24 is virtually invisible to the naked eye when gazing at anend ofthe tube.

The capillary tube 24 with its minute bore 26 provides a high resistanceto flow therethrough. An increase or decrease in the length of tube 24will decrease or increase the rate of flow in a linear fashion. Sincethis flow is laminar, Poiseuilles law is applicable, and therefore smallvariations in the radius of the bore 26 in the resistance tube willcause relatively large variations in the amount of flow. In calculatingflow through the system, not only the resistance afforded by the tube 24must be considered, but the resistances of the catheter and the filter 4must also be taken into consideration. Those resistances are known, thatof the catheter being relatively high, namely about eighty millimetersof mercury per cubic centimeter per minute, and that of the 0.22 micronfilter is millimeters of mercury per cubic centimeter per minute. By wayof example, using a resistance tube having a bore of a diameter of 0.05millimeter and a length of l centimeter, with 300 millimeters of mercurypressure on the infusion solution source 2 a flow of 3 cubic centimetersper hour is obtained, and the effective resistance of the infusionsystem would be about 6,000 milli-meters of mercury per cubic centimeterper minute. Back pressure from the patients body has no adverse effecton the flow, and a flow of about 3 cubic centimeters per hour willconstantly flush the catheter to avoid any occlusion therein, and willnot interfere with or lessen the high quality of the clinical recordingof the central arterial pulse waveforms.

Obviously, to initially fill the system by way of such a small flowthrough the resistance tube would require an objectionable amount oftime. To that end, means are provided in the passage 19 to provide for arapid flushing or quick filling of the entire system. Such meanscomprise a valve 27 of resilient material, such as rubber or syntheticrubber, which seats on the seat 21. The valve has a cylindricalextension 28 extending from the valve body and the outer end of thisextension is seatingly engaged over aninwardly extending nipple 29 onthe cap 13. The length of the valve body and extension 28 is slightlygreater than the distance from the valve seat to the cap 13 so that thevalve is sealed against its seat under its own pressure and blocks anybypassing of solution through the passages 20 and 21. The valve isactuated manually by means of a valve stem 30 extending from the valvebody through the extension and through the cap 13. When that valve stemis manually pulled outwardly the valve is drawn away from the seat 21opening the bypass and the extension 28 of the valve will assume acorrugated effect as indicated at 31 in FIG. 5. The structure of thevalve makes it fail-safe, in that it cannot accidentally be left in openposition because when the stem 30 is released the valve willautomatically and forcefully close quickly. The valve will also seataccurately because of a guiding projection 34 extending from the valvebody into the smaller passage 20.

In use, the flow control device 1 is extremely efiicient. Prior to theinsertion of the catheter in the patients body, but after the connectionof the device 1 to the pressurized infusion solution source, the stem ofthe valve 30 is pulled to open the valve and flush out the systemincluding the catheter so as to eliminate any possible air bubbles.During such flushing infusion solution will follow the line of arrows 32through the bypass passageways and out the fitting 6. The valve isclosed after the initial flushing out, but the catheter may be insertedin the patients body while the flow flushing infusion through theresistance tube 24, as indicated by the arrows 33 in FIG. 2, continues.The fitting 9 is, of course, connected to whatever indicating orrecording means may be desired, or to a pressure transducer foroscilloscopic observations, and the catheter will be maintained patentthroughout a long interval of time. It is essential for assuringwaveform quality to determine the dynamic response of the entire systemfrom time to time. This is simply accomplished by opening the valve 27and permit it to quickly close. Such a rapid flush will cause what istermed a square wave to appear on an oscilloscope and such will notmislead the observer nor will it confuse any permanent record. The valveis amply rapid in its action to perform that function.

During the use of the instant flow control and flushing device 1, therecan be no backflow because the blood pressure of the patient isinsufficient to force liquid through the capillary tube 24 in thereverse direction. The device is extremely light in weight, highlyefiicient as to its functioning, eliminates complicated setups ofapparatus, and makes it possible to monitor the central arterial pulsewaveform with its various derived parameters with much greater ease,flexibility and accuracy than was heretofore possible. Also, the deviceis sufficiently economical to warrant its disposition along with thecatheter after a single usage, if such may be indicated, although thedevice may be repeatedly used, sterilized if deemed necessary, if theconditions of the patients permit.

What we claim is:

1. A continuous flow control apparatus highly desirable for use in aliquid flow system for pressure monitoring of hemodynamics, such systemincluding a catheter which must be kept patent by continuous flushingwhen in use, comprising a block having passages therein definingcontinuously open inlet-outlet path through the block,

a flow resistor in the form of a marine-bore capillary tube in said pathto limit flow of liquid under pressure therethrough to a desired minimumamount,

said block having other passages therein defining a by-pass around thepan of said path containing said resistor which by-pass is of a size topermit a fast flow of liquid,

said by-pass being interiorly shaped to provide a valve seat,

and

a resilient valve means having a stem projecting out of said blockpositioned in said by-pass and so mounted as to forcefully press againstsaid valve seat and automatically and instantaneously close when saidstem is released.

2. The apparatus of claim 1 wherein said block is less than 1 inch inany direction and sufficiently light in weight to be suspended in afluid line.

3. The apparatus of claim 1, including a flexible tube anchored at oneend in said path, and

a fitting on the other end of said tube for connection to a pressurizedfluid source.

4. The apparatus of claim 1, wherein said valve comprises a solid bodyshaped to fit against said valve seat, and

a tubular extension on said body sealed at its outer end and which iscompressible when the valve is opened.

5. The apparatus of claim 1, including a hollow nipple projecting fromsaid block into said by-pass at the end opposite said valve seat, and

said valve comprises a solid body shaped to fit against said valve seat,and

a tubular extension on said body sealed around said nipple and which iscompressible to open said valve.

6. The apparatus of claim 5, wherein said valve and extension areslightly longer than the space occupied whereby there is continuouspressure urging the valve against said seat, and

said stem extends from the valve body through said extension foractuating said valve.

7. The control apparatus of claim 6 wherein said valve body,

extension and stem are all integral.

8. The control apparatus of claim 1, wherein said block has a passagetherethrough with one end thereof in communication with the outlet endof said path, and

a fitting at the other end of the last said passage for connection tomonitoring means or to be plugged for hypodermic injection.

9. The'control apparatus of claim 1, wherein said resistor is sized topermit a flow not exceeding 4 cubic centimeters per hour.

10. The control apparatus of claim 1, wherein said by-pass narrows atone point to form said valve seat,

and

a guide projection on said valve extends through the valve seat into thenarrower part of said by-pass to insure accurate seating of the valve.

1. A continuous flow control apparatus highly desirable for use in aliquid flow system for pressure monitoring of hemodynamics, such systemincluding a catheter which must be kept patent by continuous flushingwhen in use, comprising a block having passages therein definingcontinuously open inlet-outlet path through the block, a flow resistorin the form of a marine-bore capillary tube in said path to limit flowof liquid under pressure therethrough to a desired minimum amount, saidblock having other passages therein defining a by-pass around the partof said path containing said resistor which bypass is of a size topermit a fast flow of liquid, said by-pass being interiorly shaped toprovide a valve seat, and a resilient valve means having a stemprojecting out of said block positioned in said by-pass and so mountedas to forcefully press against said valve seat and automatically andinstantaneously close when said stem is released.
 2. The apparatus ofclaim 1, wherein said block is less than 1 inch in any direction andsufficiently light in weight to be suspended in a fluid line.
 3. Theapparatus of claim 1, including a flexible tube anchored at one end insaid path, and a fitting on the other end of said tube for connection toa pressurized fluid source.
 4. The apparatus of claim 1, wherein saidvalve comprises a solid body shaped to fit against said valve seat, anda tubular extension on said body sealed at its outer end and which iscompressible when the valve is opened.
 5. The apparatus of claim 1,including a hollow nipple projecting from said block into said by-passat the end opposite said valve seat, and said valve comprises a solidbody shaped to fit against said valve seat, and a tubular extension onsaid body sealed around said nipple and which is compressible to opensaid valve.
 6. The apparatus of claim 5, wherein said valve andextension are slightly longer than the space occupied whereby there iscontinuous pressure urging the valve against said seat, and said stemextends from the valve body through said extension for actuating saidvalve.
 7. The control apparatus of claim 6 wherein said valve body,extension and stem are all integral.
 8. The control apparatus of claim1, wherein said block has a passage therethrough with one end thereof incommunication with the outlet end of said path, and a fitting at theother end of the last said passage for connection to monitoring means orto be plugged for hypodermic injection.
 9. The control apparatus ofclaim 1, wherein said resistor is sized to permit a flow not exceeding 4cubic centimeters per hour.
 10. The control apparatuS of claim 1,wherein said by-pass narrows at one point to form said valve seat, and aguide projection on said valve extends through the valve seat into thenarrower part of said by-pass to insure accurate seating of the valve.